1. Field of the Invention
The present invention relates to a backlight unit having a protection circuit using induced voltage detection, and more particularly, to a backlight unit having a protection circuit using induced voltage detection that determines whether a lamp performs an abnormal operation by detecting a voltage induced in a power conversion transformer.
2. Description of the Related Art
In recent years, liquid crystal displays (LCDs) have received a lot of attention in that they can be reduced in size and weight as compared with the existing displays. Among the LCDs, especially LCD TVs have attracted attention. The LCD includes a backlight unit that emits light.
FIG. 1 is a configuration view illustrating a backlight unit according to the related art.
Referring to FIG. 1, a backlight unit according to the related art includes an inverter 10, a lamp group 20, adetection circuit 30, and a determination circuit 40. The inverter 10 includes a switching part 11 that switches DC power and a power conversion transformer 12 that converts the switched power into AC power that is required for driving lamps. The lamp group 20 includes a plurality of lamps each of which receives the AC power from the inverter 10 to emit light. The detection circuit 30 detects voltages that are supplied to the individual lamps from output terminals of the power conversion transformer 12. The determination circuit 40 compares each of the voltages that are detected by the detection circuit 30 with a reference voltage that is set beforehand so as to determine an abnormal operation of each of the lamps.
The detection circuit 30 that is used in the backlight unit according to the related art includes a plurality of detection elements C1, C2, C3, and C4 and a plurality of stabilizing elements C5, C6, C7, and C8.
Pairs of the detection elements C1, C2, C3, and C4 and the stabilizing elements C5, C6, C7, and C8 are connected in series with each other. The pairs are individually connected in parallel with the output terminals of the power conversion transformer 12.
The detection circuit 30 that is connected to the output terminals of the power conversion transformer 12 detects a voltage that is transmitted to each of the lamps, and transmits the detected voltage to the determination circuit 40. The detection circuit 40 compares the voltage detected by the detection circuit 30 with the reference voltage set beforehand so as to determine whether the corresponding lamp performs an abnormal operation. When the lamp performs the abnormal operation, the power conversion transformer 12 controls a switching operation of the switching part 11 of the inverter 10 to thereby cut off power supply of the inverter 10.
Each of the plurality of detection elements C1, C2, C3, and C4 of the detection circuit 30 may use a high-voltage discrete capacitor or a pattern capacitor to detect the voltage that is transmitted from the power conversion transformer 12 to each of the lamps.
When the voltage transmitted to each of the lamps is detected by using the high-voltage discrete capacitor, a circuit area is reduced as required to mount the high-voltage discrete capacitor. Further, since the high-voltage discrete capacitor is expensive, and a process of mounting the high-voltage discrete capacitor is required, manufacturing costs are increased.
When the pattern capacitor is used to detect the voltage transmitted to each of the lamps, a double sided printed circuit board is required in order to use the pattern capacitor. Further, the pattern capacitor needs to be formed of CTI 600 so that the double sided PCB has a desired dielectric constant, which results in an increase in manufacturing costs.